As resin starting materials for use in production of a reinforced plastic molding (hereinafter merely referred to as "FRP"), thermoplastic resins such as a polyethylene phthalate or a polybutylene phthalate, and thermosetting resins such as an unsaturated polyester resin or an epoxy resin have heretofore been used. In recent years, it has been required for FRP to have an excellent heat resistance and it is now necessary to develop resin starting materials for such a heat resistant FRP.
Various resin starting materials have been proposed for this purpose. FRP produced using these resin starting materials, however, do not satisfy both the requirements of a heat resistance and a toughness inherent therein. For example, if a compound having a heterocyclic ring such as an isocyanurate ring is blended to increase the heat resistance, the heat resistance of the resulting FRP is improved but its toughness deteriorates. In many resin starting materials, it is necessary to use solvents in preparation of the desired FRP, and their pot lives are short. Those suffer from the disadvantage that the workability is poor.